Seawater is 832 times denser than air, which means that a 5 knot current has more kinetic energy than a 350 km/h wind. Schemes are known to have underwater turbines situated in coastal areas with high tidal currents, such as the scheme run by Marine Current Turbines, of Bristol UK, at Strangford Lough in Northern Ireland. Here turbine blades 15 to 20 meters across are caused to rotate at 10-20 revolutions per minute by the action of tidal currents. One prototype is operational in Strangford Narrows, Northern Ireland, and uses twin 16 m diameter rotors to develop a rated power of 1.2 MW at a current velocity of 2.4 m/s. This leads to an effective efficiency in turning the kinetic energy of the water into electricity of 43% for the whole turbine system.
However, the deployment of such projects is dependent upon local coastal conditions generating suitable tidal currents, and is not suitable, for example in deepwater, off shore. There is therefore a need for a deep water solution to generate electricity using water driven turbines, and which:
1) can be deployed in waters without significant natural currents; and
2) has a high power output m2 of utilized sea bed.
Buoyancy generators are known in the art from WO2009/026610, GB2456798, US2006/017292, GB507093 and US2005188691.